Inductor bobbin



Dec. 22, 1964 FIG.5 WW

FIG.2

ATTORNEYS FIG. 3

United States Patent Office 3,152,830 Patented Dec. 22, 1964 3,162,830 INDUCTOR BOBBIN Albert Zack, Danvers, and Howard Stanton, Jr., Ipswich, Mass, assignors to Sylvania Electric Products, End, a corporation of Delaware Filed Dec. 9, 1960, Ser. No. 74,960 8 Claims. (Cl. 33628) This invention relates in general to inductors and in particular to inductors having insulating bobbins which contain and insulate windings.

In conventional manufacturing of inductors, especially transformers, it is the practice to surround a portion of the core of the device with an insulating bobbin or sleeve. Such bobbins are commonly made of kraft paper, nylon, or other plastic, ceramic, asbestors, fiberglass or the like. These materials serve the function of insulation quite well, but they lack other desirable features such as physical strength, the ability to conduct heat and versatility, since each of the numeroustransformer designs requires a particular size and configuration of bobbin. Insofar as physical strength is concerned, a particular problem arises in connection with direct-wound transformers. In these structures, the Wire coils are wound on the core of the transformer itself rather than being Wound elsewhere and assembled as a unit onto the core. In carrying out this process, a split bobbin must be fitted to the core, and the two sections must then be taped or otherwise fastened together. Such structure is, of course, inherently lacking in structural rigidity. Moreover, the thickness of the stock from which the bobbin is made becomes excessive adding to bulk and weight because loose tolerances and heavy materials must be used to compensate 'for the undesirable physical characteristics of conventional bobbins.

A most important fault in inductors constructed in accordance with present concepts stems from the inability of the bobbin to conduct and transfer heat generated by the coil and the core of the unit. This fault compels the use of very heavy windings in inductors designed to handle large currents. Indirectly, it also results in an unwieldy and physically unsound structure in which the coil or coils are largely unsupported as they bulk out from the core.

It is therefore an object of the present invention to improve inductors, particularly transformers.

It is another object of the present invention to provide transformers of smaller size but of ratings equal to those of transformers presently being made.

It is a further object of the present invention to reduce the operating temperature of inductors.

It is a still further object of the present invention to provide a more stable and rugged design for transformers.

In general. the present invention is organized about an inductor having a metallic bobbin stamped in a desired pattern from metal and coated on certain of its surfaces with resin, plastic or varnish. The bobbin may be in two pieces joined by laminations of the inductor core, or it may be a single self-supported member.

In either case, uncoated surfaces of the bobbin are placed in intimate contact with laminations which make up the core of the device. In some instances, it is desirable to actually weld the bobbin to adjacent laminations. The bobbin includes in addition to the portion which is in intimate contact with the laminations a set of flanges extending outwardly from that portion. These flanges serve to contain the coil which is subsequently wound upon the structure to form the inductor. On those areas of the bobbin which are in contact with the coil, insulation is obtained preferably by use of resin coating, although other plastics or varnishes are adequate in many a structure is useful where the winding is made external cases. Space is provided on the flanges for the addition of cooling fins or other radiating surfaces. For a better understanding of the present invention together with further objects, advantages and features, reference should be made to the following specification which should be read in conjunction with the drawings, in which:

FIG. 1 is an exploded view, partially cut away, of a transformer having a bobbin which contains two sets of laminations;

FIG. 2 is a side elevation of one of the bobbin members of FIG. 1;

FIG. 3 is an end elevation of the same bobbin member;

FIG. 4 is a side elevation of a self-supported bobbin; and

FIG. 5 is an end elevation of the same self-supported bobbin.

The inductor illustrated in FIG. 1 is a transformer utilizing formed core laminations, and the invention will be explained in connection with such an embodiment. However, the invention may also be applied to inductors of any kind, including those in which stacked E-I laminations are used and those which utilize C-cores. In FIG. 1, however, there is shown a pair of similar bobbin members 12, preferably made of cold rolled steel stampings.

The ends of the two similar bobbin members extend outwardly and are bent to form flanges 16. Central openings are formed in the bobbin members to accommodate similar sets of laminations 1S and 2d. The ends of the innermost lamination of the group 18 are preferably welded to the adjacent surfaces of the bobbin members. Similarly, the ends of the innermost lamination of the group 20 are welded to corresponding surfaces of the bobbin members adjacent the central opening. In this fashion, thermal contact surfaces, of which the surface 21 is typical, are formed between the laminated core and the bobbin members.

A coil or coils 25 are wound upon the outer periphery of the structure 25 formed by the enclosed portions of the lamination groups 18 and 20. In order to provide suitable electrical insulation between the enclosed portion 25' and the innermost windings of the coil 26, insu1ation is provided on the exterior surface of the enclosed portion 25. One of the most suitable substances from which the insulation may be made is epoxy resin, with which the outer surface of the enclosed portion 25 is fluidized. The fluidizing operation is also carried out to the extent that the inner surfaces of the flanges 16 adjacent the enclosed portion 25 and which come in contact with the coil 26 are also fluidized with resin. Materials such as Teflon, nylon or vinyl may also be used for the necessary insula tion. In fact, simple varnishes are adequate in some situations where voltages are not extreme.

The ends of the lamination groups 18 and 20 are composed of alternate long and short extensions to permit the interleaving therewith of similarly arranged lamination groups 27 and 28 to complete the inductor structure.

In FIGS. 2 and 3, one of the bobbin members is illustratedas it appears before it is assembled with the lamination groups. It will be noted that a slot is provided through the flanges at one end of the bobbin side members. This slot serves the dual purpose of preventing the flange from acting as a shorted turn and further permits the assembly of the laminations into the bobbin side members without the need for distorting the side members during the assembly process. The slot is, of course, un-

necessary in D.C. units.

In FIGS. 4 and 5, a modification of the basic structure is illustrated. In this instance, a self-supported bobbin is provided in which the laminations themselves are not utilized as a component of the bobbin proper. Such 

1. AN INDUCTOR COMPRISING A CORE COMPOSED OF A PLURALITY OF LAMINATIONS FORMED INTO A CLOSED CONFIGURATION AND HAVING A PAIR OF OPENINGS THERETHROUGH, A PORTION OF SAID LAMINATIONS FORMING A CENTRAL LEG ACROSS SAID OPENING, AT LEAST ONE METALLIC BOBBIN SURROUNDING SAID CENTRAL LEG AND IN INTIMATE CONTACT THEREWITH, SAID BOBBIN INCLUDING FLANGES EXTENDING OUTWARDLY AND PERPENDICULARLY FROM THE PORTION THEREOF SURROUNDING SAID CENTRAL LEG, SAID CENTRAL LEG HAVING END PORTIONS EXTENDING IN A DIRECTION PARALLEL TO SAID FLANGES, INSULATING MATERIAL DISPOSED UPON THE OUTER SURFACES OF SAID CENTRAL LEG, SAID PORTION OF SAID BOBBIN SURROUNDING SAID CENTRAL LEG, AND UPON THE INNER SURFACES OF SAID FLANGES, AND AT LEAST ONE COIL WOUND ABOUT SAID CENTRAL LEG AND SAID PORTION OF SAID BOBBIN SURROUNDING SAID CENTRAL LEG AND CONTAINED BY AND SUBSTANTIALLY WITHIN SAID FLANGES. 